The utilization of useful CO2 as a carbon source for the production of chemical consumables is a prime challenge with the aim both of decreasing its accumulation in the atmosphere and of curtailing our dependence on fossil fuels.
The greatest challenge facing scientists and industrialists is to recycle CO2 that is, to develop reactions which allow the production of chemical compounds, examples being fuels, polymeric plastics, drugs, detergents, and bulk molecules, which have traditionally been obtained by petrochemical methods. The technical difficulty lies in the development of chemical reactions which functionalize the CO2 while reducing the carbon center (i.e., by replacing the C—O bonds in the CO2 with C—H or C—C bonds).
Owing to the high thermodynamic stability of carbon dioxide, converting it into new chemical consumables necessarily involves an external energy source, so as to promote the thermodynamic balance of the chemical conversion, which is shown in FIG. 1.
The entirety of the efforts made by the scientific community is presently focused on the use of electricity or light to perform the electroreduction or photoreduction of CO2 into formic acid, methanal, methanol, and methane (Morris, A. J., Meyer, G. J., Fujita, E., Accounts Chem Res 2009, 42, 1983). Accordingly, this field of research is the subject of intense international competition.
A recent article describes how the use of silane compounds makes it possible to reduce CO2 under organocatalytic conditions (Riduan, S, N., Zhang, Y. G., Ying, J. Y., Angewandte Chemie—International Edition 2009, 48, 3322). In this case, the silane compound is the high-energy reactive species, and the use of the catalyst promotes the kinetic balance. The authors describe the formation of silyl products of formyl (SiOCHO), acetal (SiOCH2OSi), and methoxy (SiOCH3) types. Although this strategy is justified by the importance of the uses of reduction products of CO2 in the chemical industry (HCOOH, H2CO, CH3OH), it should nevertheless be noted that these molecules are currently used on a scale which remains very low in relation to the amount of useful CO2 available. In other words, if these molecules were to be produced exclusively from CO2, they would allow the utilization, on the basis of the current market, of only 3.4% of the useful CO2 produced each year (2.5 Gt/year) (Panorama des voies de valorisation du CO2, ADEME, June 2010, http://www2.ademe.fr/servlet/getDoc?cid=96&m=3&id=72052&p1=30&ref=12441). It is therefore necessary to look at diversifying the nature and number of chemical consumables that are obtainable from CO2.
Another strategy in converting CO2 into new chemical consumables involves using a reactive chemical partner (high in energy) to promote the thermodynamic balance of the chemical conversion of CO2. This strategy is presently not widely represented within the scientific landscape, but it will, eventually, allow a considerable expansion in the range of molecules available from CO2. The only industrial process based on this approach is the synthesis of urea obtained by condensing ammonia with CO2, as indicated in equation 1 below (Sakakura, T., Choi, J. C., Yasuda, H., Chem Rev 2007, 107, 2365).

Following the same principle, the synthesis of polycarbonates by CO2/epoxide copolymerization is undergoing industrialization, as indicated in equation 2 below (Panorama des voies de valorisation du CO2, ADEME, June 2010, http://www2.ademe.fr/servlet/getDoc?cid=96&m=3&id=72052&p1=30&ref=12441).

In these two syntheses (equations 1 and 2), there is no formal reduction of the carbon center of CO2.
Still with the aim of obtaining new chemical compounds, it is possible to consider converting the CO2 into formamide compounds. Formamide compounds are a class of chemical compounds which are important in the chemical industry, in which they are presently used as solvents, reagents, and precursors to plastics (The Amide Linkage: Structural Significance in Chemistry, Biochemistry, and Materials Science, Greenberg, A. B., C. M., Liebman, J. F.; Wiley-Interscience: Hoboken, N.J., 2002). Formamide compounds (of general formula R1R2NCHO) are generally synthesized by condensing amines with formic acid.
N,N-Dimethylmethanamide (also called dimethylformamide), which is the most commonly used formamide compound, given that it serves as a polar solvent, is produced industrially by reacting dimethylamine with carbon monoxide under catalytic conditions (The Amide Linkage: Structural Significance in Chemistry, Biochemistry, and Materials Science, Greenberg, A. B., C. M., Liebman, J. F.; Wiley-Interscience: Hoboken, N.J., 2002).
Formamide compounds may also be obtained starting from carbon dioxide instead of carbon monoxide, which is toxic. This alternative pathway rests on the synthesis of the formamide compounds by reaction of carbon dioxide, dihydrogen, and an amine in the presence of transition metal complexes as catalyst (Schreiner, S., Yu, J. Y.; Vaska, L., Inorganica Chimica Acta 1988, 147, 139; Schreiner, S., Yu, J. Y., Vaska, L. Journal of the Chemical Society—Chemical Communications 1988, 602; Vaska, L., Schreiner, S., Felty, R. A., Yu, J. Y., Journal of Molecular Catalysis 1989, 52, L11; Yu, J. Y., Schreiner, S., Vaska, L. Inorganica Chimica Acta 1990, 170, 145; Jessop, P. G., Hsiao, Y., Ikariya, T., Noyori, R., Journal of the American Chemical Society 1994, 116, 8851; Jessop, P. G., Hsiao, Y., Ikariya, T., Noyori, R. Journal of the American Chemical Society 1996, 118, 344; Munshi, P., Heldebrant, D. J., McKoon, E. P., Kelly, P. A., Tai, C. C., Jessop, P. G., Tetrahedron Letters 2003, 44, 2725); Schmid, L., Rohr, M., Baiker, A., Chemical Communications 1999, 2303; Federsel, C., Boddien, A., Jackstell, R., Jennerjahn, R., Dyson, P. J., Scopelliti, R., Laurenczy, G., Beller, M., Angew. Chem. Int. Ed. 2010, 49, 9777; Liu, J., Guo, C., Zhang, Z., Jiang, T., Liu, H., Song, J., Fan, H., Han, B., Chemical Communications 2010, 46, 5770. This pathway has numerous drawbacks, more particularly the following:                the choice of starting amine is very limited: dimethylamine, diethylamine, piperidine, and aniline (Schreiner, S., Yu, J. Y.; Vaska, L., Inorganica Chimica Acta 1988, 147, 139; Schreiner, S., Yu, J. Y., Vaska, L. Journal of the Chemical Society—Chemical Communications 1988, 602; Vaska, L., Schreiner, S., Felty, R. A., Yu, J. Y., Journal of Molecular Catalysis 1989, 52, L11; Yu, J. Y., Schreiner, S., Vaska, L. Inorganica Chimica Acta 1990, 170, 145; Jessop, P. G., Hsiao, Y., Ikariya, T., Noyori, R., Journal of the American Chemical Society 1994, 116, 8851; Jessop, P. G., Hsiao, Y., Ikariya, T., Noyori, R. Journal of the American Chemical Society 1996, 118, 344; Munshi, P., Heldebrant, D. J., McKoon, E. P., Kelly, P. A., Tai, C. C., Jessop, P. G., Tetrahedron Letters 2003, 44, 2725); Schmid, L., Rohr, M., Baiker, A., Chemical Communications 1999, 2303; Federsel, C., Boddien, A., Jackstell, R., Jennerjahn, R., Dyson, P. J., Scopelliti, R., Laurenczy, G., Beller, M., Angew. Chem. Int. Ed. 2010, 49, 9777; Liu, J., Guo, C., Zhang, Z., Jiang, T., Liu, H., Song, J., Fan, H., Han, B., Chemical Communications 2010, 46, 5770;        the CO2 and H2 pressure required is generally high: from 100 to 250 bar and at 100° C. (except for a platinum system which is active at ambient temperature under a pressure of 1 bar, described by Schreiner, S., Yu, J. Y., Vaska, L., Journal of the Chemical Society—Chemical Communications 1988, 602);        this pathway requires the use of transition metal complexes which are often expensive (Ir, Ru, Rh, Pt, Cu, Fe);        the use of an organic solvent is generally required, except for a few isolated examples of reactions in supercritical CO2 (Jessop, P. G., Hsiao, Y., Ikariya, T., Noyori, R., Journal of the American Chemical Society 1994, 116, 8851; Jessop, P. G., Hsiao, Y.; Ikariya, T., Noyori, R., Journal of the American Chemical Society 1996, 118, 344; Krocher, O., Koppel, R. A., Baiker, A., High Pressure Chemical Engineering 1996, 12, 91; Kayaki, Y., Suzuki, T., Ikariya, T. Chemistry Letters 2001, 1016; Liu, F. C., Abrams, M. B., Baker, R. T., Tumas, W., Chemical Communications 2001, 433; Kayaki, Y., Shimokawatoko, Y., Ikariya, T., Advanced Synthesis & Catalysis 2003, 345, 175), and of one example in ionic liquid (Liu, F. C., Abrams, M. B., Baker, R. T., Tumas, W., Chemical Communications, 2001, 433), and of one example without solvent (Krocher, O., Koppel, R. A., Baiker, A., Chemical Communications 1997, 453);        the addition of additives (carbon, oxygen, or nitrogen bases) is necessary in order to accelerate the reaction or improve the yields and selectivities (Munshi, P., Heldebrant, D. J., McKoon, E. P., Kelly, P. A.; Tai, C. C., Jessop, P. G. Tetrahedron Letters 2003, 44, 2725).        
In the context of the synthesis of formamide compounds using carbon dioxide, the technical challenge to be answered is to couple the functionalization of the carbon dioxide with a step of chemical reduction. In order to maximize the energy yield of such a conversion, it is necessary to develop reactions having a limited number of steps (ideally just one), and catalyzed, in order to prevent energy losses of kinetic order.
Moreover, labeled formamide compounds, incorporating stable isotopes and/or radio isotopes, is of particular interest in numerous sectors, such as, for example, in the life sciences (study/elucidation of enzymatic mechanisms, biosynthetic mechanisms, in biochemistry, etc.), environmental sciences (tracing of wastes, etc.), research (study/elucidation of reaction mechanisms), or else research and development of new pharmaceutical and therapeutic products. Accordingly, developing a synthesis for preparing labeled formamide compounds meeting the requirements indicated above can respond to a genuine need.
There is therefore a genuine need for a process for preparing formamide compounds by conversion of CO2 that overcomes the drawbacks of the prior art, said process allowing the functionalization of the carbon dioxide to be coupled with a step of chemical reduction.
In particular, a genuine need exists for a process which produces the formamide compounds in a single step and with an excellent selectivity, from CO2 and amines, under catalytic conditions, and in the presence of a compound which ensures the reduction of CO2.
Moreover, there exists a genuine need to have a process which produces, in a single step and with an excellent selectivity, labeled formamide compounds incorporating stable isotopes and/or radio isotopes, starting from labeled reagents such as, for example, labeled CO2 and/or labeled amines, under catalytic conditions and in the presence of a compound which ensures the reduction of CO2.